Where have you looked?
Soon as I've had my first service, I want to investigate the wiring to the steering wheel controls. The steering wheel mute is useless, because it is toggle on/off, but I want to see what happens if I simulate a seventh button.
trabbic posted in the "Subaru OEM Plug-n-Play Bluetooth Phone Module! " thread that he saw a "CALL" message on the radio displayed when he was poking around the rear connectors, but is not sure how he got it.